Electronic nematicity is a state of matter in which rotational symmetry is spontaneously broken and translational symmetry is preserved. In strongly correlated materials, nematicity often emerges from fluctuations of a multicomponent primary order, such as spin or charge density waves, and is termed vestigial nematicity. One widely studied example is Ising nematicity, which arises as a vestigial order of collinear antiferromagnetism in the tetragonal iron pnictide superconductors. Because nematic directors in crystals are restricted by the underlying crystal symmetry, recently identified quantum materials with three-fold rotational symmetry offer a new platform to investigate nematic order with three-state Potts character. Here we demonstrate strain control of three-state Potts nematicity as a vestigial order of zigzag antiferromagnetism in FePSe₃. Optical linear dichroism measurements reveal the nematic state and demonstrate the rotation of the nematic director by uniaxial strain. We show that the nature of the nematic phase transition can also be controlled by strain, inducing a smooth crossover transition between a Potts nematic transition and an Ising nematic flop transition. Elastocaloric measurements demonstrate the signatures of two coupled phase transitions, indicating that the vestigial nematic transition is separated from the antiferromagnetic transition. This establishes FePSe₃ as a system to explore three-state Potts vestigial nematicity.

电子向轴性是一种物质状态，在这种状态中，旋转对称性自发地被打破，平移对称性被保留。在强相关材料中，向向性通常来自多组分初级的波动，例如自旋波或电荷密度波，这被称为退化向向性。一个被广泛研究的例子是 Ising 向磁性，它在四方铁镍晶超导体中作为共线反铁磁性的退化顺序出现。由于晶体中的向列导向度受到潜在晶体对称性的限制，最近发现的具有三重旋转对称性的量子材料为研究具有三态 Potts 特性的向列顺序提供了一个新平台。在这里，我们证明了三态 Potts 向向性的应变控制作为 FePSe₃ 中锯齿形反铁磁性的退化顺序。光学线性二向色性测量揭示了向列状态，并证明了单轴应变对列导向器的旋转。我们表明，向列相变的性质也可以通过应变来控制，从而在 Potts 向列相变和 Ising 向列翻转相变之间诱导平滑的交叉转变。弹性热量测量证明了两个耦合相变的特征，表明残留的向列转变与反铁磁转变是分开的。这确立了 FePSe₃ 作为探索三态 Potts 残余向轴性的系统。